Method for preparing high-purity metallic tin by using vacuum distillation technology

Abstract

A method for preparing high-purity metallic tin by using a vacuum distillation technology belongs to the technical field of high-purity metallic tin preparation, and comprises the following steps: mechanically crushing a tin ingot, scrubbing oxide skin, and carrying out vacuum drying to obtain a pretreated tin material; the pretreated tin material is placed in a graphite crucible to be subjected to vacuumizing and heating treatment, so that high-vapor-pressure impurities are volatilized along with tin vapor, and primary tin vapor is obtained after the high-vapor-pressure impurities are captured through a cold trap; and the primary tin steam is guided to flow through the main condensation area for condensation treatment, and a secondary tin ingot is obtained. And the secondary tin ingot is placed in a graphite crucible to be subjected to vacuumizing and heating treatment, iterative distillation refining is conducted on the secondary tin ingot, and the high-purity metallic tin is obtained. According to the method, high-vapor-pressure impurities and tin vapor can be separated to a large extent, and the purity of prepared metallic tin is guaranteed by combining iterative refining and tin purity inspection of tin materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-purity metallic tin preparation, and more specifically, relates to a method for preparing high-purity metallic tin by utilizing vacuum distillation technology. Background Art

[0002] High-purity tin, an emerging functional material, is widely used in alloy manufacturing for aerospace applications, semiconductor materials for electronic information, and other fields, becoming a key material supporting humanity's high-tech development. Currently, the main methods for preparing high-purity tin include electrolysis and chlorination. These methods have high requirements for raw materials and require numerous tedious chemical processes such as oxidation, chlorination, and reduction electrolysis. These processes produce large amounts of metal compounds, wastewater, and exhaust gases, significantly impacting the ecological environment, causing significant resource waste and low labor productivity.

[0003] At present, some existing methods for preparing high-purity tin first prepare tin tetrachloride, then synthesize tin hydroxide after fractional distillation and purification, and then obtain high-purity tin through hydrogen reduction. This method has a long process and needs to go through chemical processes such as chlorination, which has a great impact on the ecological environment and is difficult to meet the requirements of green metallurgy. Others use metallic tin with a content of ≥99.99% as raw material, and obtain high-purity tin powder through vacuum melting and centrifugal atomization. This method has strict requirements on raw materials and only changes the material morphology, which is difficult to provide guidance for the production process of high-purity tin. Therefore, the traditional smelting-electrolysis process has high energy consumption and limited impurity removal rate, making it difficult to economically obtain a purity of 5N or above, and it is easier to introduce secondary oxidation impurities during the operation. Summary of the Invention

[0004] In order to address the deficiencies in the prior art, the present invention aims to solve the above-mentioned defects and further propose a method for preparing high-purity metallic tin using vacuum distillation technology.

[0005] The present invention adopts the following technical solutions.

[0006] The first aspect of the present invention discloses a method for preparing high-purity metallic tin using vacuum distillation technology, the method comprising: The tin ingot is mechanically crushed and the oxide scale is brushed off, and then vacuum dried to obtain the pretreated tin material; The pretreated tin material is placed in a graphite crucible for vacuuming and heating, so that high vapor pressure impurities are volatilized along with the tin vapor, and the high vapor pressure impurities are captured by a cold trap to obtain primary tin vapor; guiding the primary tin vapor to flow through a primary condensation zone for condensation to obtain a secondary tin ingot; The secondary tin ingot is placed in a graphite crucible for vacuuming and heating, so as to perform iterative distillation and refining on the secondary tin ingot to obtain high-purity metallic tin.

[0007] Furthermore, the tin ingot is mechanically crushed and the oxide scale is brushed, and then vacuum dried to obtain the pretreated tin material, comprising: placing the tin ingot in a jaw crusher with a polyurethane liner, adjusting the gap between the movable jaws, crushing the tin ingot, and separating the iron scraps in the crushed tin ingot by magnetic separation; The crushed tin block is placed in a drum scrubber for scrubbing to remove the oxide scale on the surface of the tin block; the oxide scale includes a SnO2 / Ox layer and salt particles.

[0008] Furthermore, the tin ingot is mechanically crushed and the oxide scale is brushed off, and the pretreated tin material is obtained after vacuum drying, and the method further includes: Placing the tin block after the oxide scale is removed in a double-chamber vacuum oven, adjusting the temperature of the double-chamber vacuum oven, and performing a vacuum drying process on the tin block to remove bound water and air in the air gap of the tin block; The vacuum-dried tin blocks are screened through a stainless steel vibrating screen to retain the tin blocks that meet the particle size requirements and put them into an argon-filled temporary storage hopper to obtain the pretreated tin material, and the tin blocks that do not meet the particle size requirements are subjected to secondary crushing treatment.

[0009] Furthermore, the pretreated tin material is placed in a graphite crucible for vacuuming and heating to volatilize high vapor pressure impurities along with the tin vapor, and the high vapor pressure impurities are captured by a cold trap to obtain primary tin vapor, comprising: The pretreated tin material is placed in a graphite crucible, and a graphite cover is covered on the top of the graphite crucible containing the pretreated tin material to seal it, and a vacuum treatment is performed; Inserting a platinum-rhodium thermocouple into a temperature control hole on the side wall of the graphite crucible to provide real-time feedback of temperature data, and uniformly heating the temperature to a preset temperature according to a heating program curve to perform constant temperature heating, thereby heating the pretreated tin material from a solid phase to a liquid phase and a gas phase; driving the tin molecules in the liquid phase and the gas phase and the high vapor pressure impurities to synchronously separate from the liquid phase by vapor pressure to separate the primary tin vapor; The graphite cover on the top of the graphite crucible is connected to the vacuum furnace chamber flange through a graphite ring sealing ring, and the high vapor pressure impurities and tin molecules enter the pipeline after leaving the liquid phase. A graphite sealing ring is provided at the joint between the pipeline and the vacuum furnace chamber to isolate air intrusion.

[0010] Furthermore, the pipeline is composed of an insulated main steam pipe and a jacketed spiral condensing coil. The insulated main steam pipe is made of stainless steel or graphite and is coated with a high-temperature resistant insulation layer. One end of the insulated main steam pipe is connected to the output port of the graphite crucible, and the other end is connected to the input port of the jacketed spiral condensing coil. The jacketed spiral condensing coil is the main condensing area, which is divided into an inner tube and an outer tube. The inner tube is used to circulate the primary tin vapor, and the outer tube is used to circulate hot oil or blow air to control the temperature, so as to control the temperature of the inner tube wall within a preset condensing temperature range.

[0011] Furthermore, the step of guiding the primary tin vapor to flow through a primary condensation zone for condensation to obtain a secondary tin ingot comprises: guiding the primary tin vapor to flow through the insulated main steam pipe and then into the jacketed spiral condensing coil, controlling the inner tube wall temperature of the jacketed spiral condensing coil to be within a preset condensing temperature range, and condensing the primary tin vapor to obtain liquid tin and residual gas; directing the residual gas through the branch of the jacketed spiral condensing coil into a cold trap to separate high vapor pressure impurities; A guide groove is provided at the bottom end of each spiral condensing coil of the jacketed spiral condensing coil, and a shovel hook type scraper is provided at the input end of the guide groove for guiding the liquid tin to flow into the cooling tank, and the secondary tin ingot is obtained after cooling and storage.

[0012] Furthermore, the jacketed spiral condensing coil has a plurality of condensing ports, which respectively correspond to different turns, different guide grooves and different cooling tanks of the jacketed spiral condensing coil; the method further comprises: Constructing a machine learning model based on the condensation temperatures, isotope ratios, and tin vapor contents corresponding to each of the plurality of condensation ports, and determining a loss function and constraints of the machine learning model based on the isotope ratios and the tin vapor contents; calling the machine learning model, taking the current condensation temperature of each condensation port as input, and outputting the corresponding isotope ratio of the tin element and the tin vapor content, so as to dynamically adjust the condensation temperature of each condensation port based on the isotope ratio and the tin vapor content; The constraint condition is used to determine the number of iterative distillation and refining times of the tin ingot.

[0013] Furthermore, the secondary tin ingot is placed in a graphite crucible for vacuuming and heating to perform iterative distillation and refining on the secondary tin ingot to obtain high-purity metallic tin, comprising: placing the secondary silver ingot in a graphite crucible for vacuuming and heating, so as to repeatedly distill and refine the secondary tin ingot to obtain refined tin vapor; The refined tin vapor is condensed under argon protection to obtain a refined tin ingot, and the tin purity of the refined tin ingot is tested by GDMS. After passing the test, the high-purity metallic tin is obtained.

[0014] Furthermore, the method further comprises: When the tin purity of the refined tin ingot does not meet the preset requirements after GDMS testing, the refined tin ingot is crushed and placed in a graphite crucible for vacuuming and heating, so as to distill and refine the refined tin ingot again until the tin purity meets the preset requirements.

[0015] The second aspect of the present invention discloses a device for preparing high-purity metallic tin using vacuum distillation technology, which is used to implement the method for preparing high-purity metallic tin using vacuum distillation technology described in the first aspect. The device includes a graphite crucible, a pipeline, a main condensation zone, and a cold trap; The graphite crucible is located at the bottom of the vacuum furnace chamber and is used to hold the pre-treated tin material; The input end of the pipeline is connected to the output end of the graphite crucible, and is divided into an insulated main steam pipe and a jacketed spiral condensing coil. The insulated main steam pipe is used to guide the tin vapor to the jacketed spiral condensing coil. The jacketed spiral condensing coil serves as the main condensing zone and is used to condense the tin vapor in different zones. The cold trap is connected to the output end of the main condensation zone and is used to adsorb high vapor pressure impurities remaining after the impurities flow through the main condensation zone.

[0016] The beneficial effects of the present invention are that, compared with the prior art, the present invention has the following advantages: (1) The present invention mechanically crushes a primary tin ingot and scrubs the oxide scale, vacuum-drying it to obtain a pretreated tin material. The pretreated tin material is then placed in a graphite crucible, vacuumed, heated, and treated. High vapor pressure impurities evaporate first along with the tin vapor and are captured by a cold trap, thereby outputting primary tin vapor. Since high vapor pressure impurities (Cd, Zn, In, Sb, etc.) are more easily vaporized than tin, they preferentially enter the gas phase, mix with the tin vapor, and flow upward along a vertical pipe to the cold trap. This allows the high vapor pressure impurities to be separated from the tin vapor to a large extent, ensuring the purity of the tin in the tin vapor and laying the foundation for the subsequent preparation of high-purity metallic tin.

[0017] (2) The present invention guides the primary tin vapor to flow through the main condensation zone and condenses it into secondary tin ingots, the purity of which has been increased to at least 4N. As the raw material for subsequent refined tin, the high-purity tin vapor is condensed under the protection of argon to form high-purity tin ingots. The tin purity is detected by GDMS. If it is qualified, it is put into storage. If it is unqualified, the high-purity tin ingot is used as a pre-treated tin material for iterative refining, thereby further ensuring the purity of the metallic tin preparation.

[0018] (3) The present invention constructs a machine learning model based on the condensation temperature of the condensation port in the main condensation zone, the isotope ratio of the tin element, and the quality of the tin vapor. At the same time, combined with the corresponding loss function and constraint conditions, the number of iterative refining of metallic tin is determined, and the condensation temperature of each condensation port can be dynamically controlled to minimize the waste of tin vapor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic flow chart of a method for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention; Figure 2 It is a structural schematic diagram of a device for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention. DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present application.

[0021] like Figure 1 As shown, in one embodiment, a method for preparing high-purity metallic tin using vacuum distillation technology includes the following steps: Step S110 , mechanically crushing the tin ingot and scrubbing the oxide scale, and vacuum drying to obtain a pretreated tin material.

[0022] In some embodiments, the method for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention, step S110 specifically includes the following steps: Step S111: placing the tin ingot in a jaw crusher with a polyurethane liner, adjusting the gap between the movable jaws, crushing the tin ingot, and separating the iron chips in the crushed tin ingot by magnetic separation.

[0023] In step S112, the crushed tin block is placed in a drum scrubber for scrubbing to remove the oxide scale on the surface of the tin block; the oxide scale includes a SnO2 / Ox layer and salt particles.

[0024] In some embodiments, the method for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention, step S110 specifically further includes the following steps: Step S113 , placing the tin block after the oxide scale is removed in a double-chamber vacuum oven, adjusting the temperature of the double-chamber vacuum oven, and performing a vacuum drying process on the tin block to remove bound water and air in the air gap of the tin block.

[0025] Step S114, sieving the vacuum-dried tin blocks through a stainless steel vibrating screen to retain the tin blocks that meet the particle size requirements and put them into an argon-filled temporary storage hopper to obtain pre-treated tin materials, and performing secondary crushing on the tin blocks that do not meet the particle size requirements.

[0026] In a specific embodiment, the method for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention is implemented by a pipeline architecture from a graphite crucible to a cold trap, and the architecture includes: Graphite crucible: placed at the bottom of the vacuum furnace chamber, used to hold the pre-treated tin block. Its exterior is heated to 1100°C by a heating tube to partially vaporize and partially melt the tin block.

[0027] Piping: A stainless steel or graphite pipe extends from the top of the graphite crucible and directly connects to the cooling section. The temperature within the pipe gradually decreases as it moves away from the crucible, first through the primary condensation zone at approximately 350-400°C, and then to the even lower cold trap. This pipe not only serves as a channel for tin vapor and impurity gases, but also provides a place for graded condensation at different temperature ranges. The pipe is arranged with multiple elbows and appropriately angled to achieve segmented airflow within the temperature gradient. This allows tin vapor to condense first in the primary condensation section, while high-vapor-pressure impurities continue along branch lines to the cold trap, effectively separating the gaseous components.

[0028] Primary Condensation Zone: This section of the pipeline is surrounded by a water-cooling jacket or electric heating jacket, and its temperature is strictly controlled at 350-400°C. When the primary tin vapor (and its small amount of impurities) emerges from 1100°C and encounters this primary condensation zone, the vapor pressure of the tin drops significantly. A large number of tin molecules preferentially condense on the pipe walls, turning back into liquid. These droplets then drip down the pipe walls into the collection tank, eventually forming secondary tin ingots. Conversely, impurities with higher vapor pressures remain in a gaseous state at 350–400°C and do not condense in this section, allowing them to continue onward.

[0029] Cold traps: Located after the primary condensation zone, the pipeline is further cooled to extremely low temperatures, often maintained with liquid nitrogen or dry ice ethanol. High-vapor-pressure impurities, while not completely condensed at 350-400°C, remain in the vapor phase and are thus guided all the way to the cold trap, where they freeze and adhere to the pipe walls or the interior of the trap. In contrast, tin vapor is almost completely trapped in the primary condensation zone, leaving only a trace tin film. If the temperature inside the cold trap is low enough, this residual tin will also form a thin tin film there.

[0030] Including steps 1 to 4: Step 1: Raw material pretreatment.

[0031] The primary tin ingot (usually 99.9% tin ingot) is mechanically crushed and the oxide scale is brushed off, and then vacuum dried to obtain the pretreated tin material.

[0032] The following steps are involved: Step 1.1, mechanical disruption.

[0033] Step 1.1 is used to increase the specific surface area and provide an activated interface for subsequent deoxidation and drying.

[0034] Specifically, the tin ingot is placed in a jaw crusher with a polyurethane liner, and the movable jaw gap is adjusted to 12 mm; after crushing, the tin ingot is passed through a magnetic separator to remove the iron chips that occasionally enter.

[0035] Step 1.2, scrub the oxide scale.

[0036] Step 1.2 is used to remove the surface SnO2 / Ox layer and salt particles to reduce the secondary oxidation source.

[0037] Specifically, the crushed tin blocks enter the drum scrubber; the body of the machine is lined with soft-bristled nylon brushes and sprayed with 2wt% citric acid deionized water; the drum speed of the drum scrubber is set to 15rpm and the time is set to 5min; the end air knife blows away the free liquid on the surface.

[0038] Step 1.3, vacuum drying for pre-degassed.

[0039] Step 1.3 is used to remove bound water and air in the air gap to prevent subsequent steam explosion and oxidation at high temperatures.

[0040] Specifically, the tin block after removing the oxide scale is placed in a double-chamber vacuum oven (mechanical pump + molecular pump, ultimate pressure 10⁻³Pa); the oven temperature can be set to 120℃ and heated at a constant temperature for 2 hours.

[0041] Step 1.4, screening and temporary storage.

[0042] Step 1.4 is used to ensure particle size consistency and traceability, providing stable loading for subsequent vacuum heating evaporation.

[0043] Specifically, the dried tin block is passed through a 20 mm stainless steel vibrating screen; the large particles on the screen are returned to step 1.1 for re-crushing, and the particles under the screen enter an argon-filled temporary storage hopper, where a code is scanned to assign a unique batch number as the pretreated tin material.

[0044] In step S120 , the pretreated tin material is placed in a graphite crucible for vacuuming and heating, so that high vapor pressure impurities are volatilized along with the tin vapor, and the high vapor pressure impurities are captured by a cold trap to obtain primary tin vapor.

[0045] In some embodiments, the method for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention, step S120 specifically includes the following steps: Step S121 , placing the pretreated tin material in a graphite crucible, covering the top of the graphite crucible containing the pretreated tin material with a graphite cover for sealing, and performing a vacuum treatment.

[0046] In step S122, a platinum-rhodium thermocouple is inserted into the temperature control hole on the side wall of the graphite crucible to provide real-time temperature data feedback, and the temperature is raised uniformly to a preset temperature according to the heating program curve for constant temperature heating, thereby heating the pretreated tin material from the solid phase to the liquid phase and the gas phase.

[0047] In step S123 , the tin molecules in the liquid phase and the gas phase are driven by the vapor pressure to synchronously separate from the liquid phase along with the high vapor pressure impurities, so as to separate the primary tin vapor.

[0048] Among them, the graphite cover on the top of the graphite crucible is connected to the vacuum furnace chamber flange through a graphite ring sealing ring, and the high vapor pressure impurities and tin molecules enter the pipeline after leaving the liquid phase. A graphite sealing ring is provided at the joint between the pipeline and the vacuum furnace chamber to isolate the air from intrusion.

[0049] In a specific embodiment, the present invention provides a method for preparing high-purity metallic tin using vacuum distillation technology, step 2, vacuum heating evaporation: the pretreated tin material is loaded into a graphite crucible, evacuated to 10⁻³Pa, and heated to 1100°C; high vapor pressure impurities are first volatilized with the tin vapor and captured by a cold trap, outputting a primary tin vapor.

[0050] In this example, vacuum distillation utilizes the differences in saturated vapor pressures of the components in the pretreated tin material at different temperatures to separate them. At the same temperature, the higher the saturated vapor pressure of a component, the more readily it evaporates. Therefore, by controlling the temperature and vacuum level, the component with the higher vapor pressure will evaporate first, while the component with the lower vapor pressure will remain in the remaining liquid phase, ultimately achieving the desired separation.

[0051] The relationship between the saturated vapor pressure of a pure substance and temperature is expressed as: ; Where A, B, C, and D are evaporation constants, p is the vapor pressure in Pa, and T represents the temperature.

[0052] In this embodiment, the saturated vapor pressure criterion shows that the order of volatilization of the components in the pretreated tin material is: As>Sb>Pb>Sn. At the same temperature, the vapor pressure values of As, Sb, and Pb are much greater than that of Sn. Therefore, under suitable distillation temperature conditions, As, Sb, and Pb will volatilize into the gas phase before Sn, i.e., the high vapor pressure impurities in this embodiment, ultimately achieving the separation of the high vapor pressure impurities from Sn.

[0053] The following steps are involved: Step 2.1, crucible loading and sealing.

[0054] Specifically, the pretreated tin material is taken out from the inert gas protection hopper and placed in a graphite crucible; a graphite cover is placed on the top of the crucible, and a graphite ring seal is used to connect it to the vacuum furnace chamber flange; the furnace chamber cover is closed, and the vacuum pump group is turned on to evacuate the air, first using a mechanical pump to pressurize the chamber to 1Pa; then the molecular pump is started to pump the total pressure to the target 10⁻³Pa.

[0055] Step 2.2: Raise the temperature to 1100°C and maintain constant temperature.

[0056] Specifically, a platinum-rhodium thermocouple is inserted into the temperature control hole on the side wall of the crucible to provide real-time temperature feedback. The resistance heating element, usually a three-stage surrounding graphite sleeve, is heated from room temperature to 1100°C at an average rate of 10°C / min according to the temperature ramp curve. After reaching 1100°C, the temperature is maintained constant for 30 minutes to ensure that the tin material is converted from solid phase to liquid phase and partially vaporized. That is, the saturated vapor pressure of tin is controlled at 0.1Pa.

[0057] In step 2.3, the high vapor pressure impurities are volatilized along with the tin vapor.

[0058] Specifically, vapor pressure drives tin molecules and high vapor pressure impurities to simultaneously separate from the liquid phase; high vapor pressure impurities (lead, bismuth, antimony, and arsenic) are easier to vaporize than tin, preferentially enter the gas phase, mix with tin vapor, and flow upward along the vertical pipe; a graphite sealing ring is used at the joint between the pipe and the furnace chamber to prevent air intrusion, and an insulating sleeve is used to maintain the temperature at the joint above approximately 1000°C, reducing premature condensation caused by hot and cold gradients.

[0059] Understandably, at the same temperature, the higher the vapor pressure, the easier it is for the corresponding substance to vaporize, and the lower the corresponding boiling point. Similarly, the lower the vapor pressure, the harder it is for the corresponding substance to vaporize, and the higher the corresponding boiling point. Therefore, the boiling point of low-vapor-pressure impurities is higher than that of tin, while the boiling point of high-vapor-pressure impurities is lower than that of tin. In this example, the high-vapor-pressure impurities are lead, bismuth, antimony, and arsenic, while the low-vapor-pressure impurities are iron and copper.

[0060] It should be noted that although the boiling points of iron and copper are close to those of tin, due to the vacuum in this embodiment (≈10 - 3 Under the conditions of 1100°C (≈1100°C), tin has a much higher vapor pressure than iron and copper. Therefore, in this example, at the same temperature as copper and iron, tin vaporizes more readily. Consequently, tin is preferentially evaporated and separated compared to copper and iron, leaving the remaining liquid phase enriched in iron and copper. Therefore, this example achieves the separation of tin from copper and iron through vacuum distillation by exploiting the vapor pressure difference.

[0061] Step 2.4, separating high vapor pressure impurities from primary tin vapor.

[0062] Specifically, after the high vapor pressure impurities flow through the main condensation zone, the tin vapor and the main condensation zone condense into a liquid phase, and the high vapor pressure impurities flow to the cold trap for condensation, thereby achieving separation between the high vapor pressure impurities and the tin vapor, thereby improving the purity of the tin vapor.

[0063] In some embodiments, the present invention provides a method for preparing high-purity metallic tin using vacuum distillation technology, wherein the pipeline is composed of an insulated main steam pipe and a jacketed spiral condenser coil. The insulated main steam pipe is made of stainless steel or graphite, and the outer layer is covered with a high-temperature resistant insulation layer. One end of the insulated main steam pipe is connected to the output port of the graphite crucible, and the other end is connected to the input port of the jacketed spiral condenser coil.

[0064] The jacketed spiral condensing coil is the main condensing area, which is divided into an inner tube and an outer tube. The inner tube is used to circulate the primary tin steam, and the outer tube is used to circulate hot oil or blower temperature control to control the temperature of the inner tube wall within the preset condensing temperature range.

[0065] Step S130 , guiding the primary tin vapor to flow through the primary condensation zone for condensation to obtain secondary tin ingots.

[0066] In some embodiments, the method for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention, step S130 specifically includes the following steps: Step S131, guiding the primary tin vapor to flow through the insulated main steam pipe and then into the jacketed spiral condenser coil, and controlling the inner tube wall temperature of the jacketed spiral condenser coil to be within a preset condensation temperature range, condensing the primary tin vapor to obtain liquid tin and residual gas.

[0067] Step S132 , guiding the residual gas into a cold trap through a branch of the jacketed spiral condensing coil to separate high vapor pressure impurities.

[0068] Step S133, a guide groove is set at the bottom end of each spiral condensing coil of the jacketed spiral condensing coil, and a shovel hook type scraper is set at the input end of the guide groove to guide the liquid tin to flow into the cooling tank, and obtain secondary tin ingots after cooling and storage.

[0069] In a specific embodiment, the present invention provides a method for producing high-purity metallic tin using vacuum distillation technology. In step 3, condensation and collection, the primary tin vapor is directed through a primary condensation zone at 350-400°C and condensed into secondary tin ingots. At this point, the purity has been raised to at least 4N, and the secondary tin ingots are used as raw material for subsequent refining.

[0070] Specifically, the above pipeline consists of two parts: the insulated main steam pipe (generally shorter, with the function of providing buffering and of course insulation) and the jacketed spiral condenser coil (i.e. the main condensing area).

[0071] The insulated main steam pipe is the high-temperature section of piping that carries tin vapor from the crucible to the primary condensing zone. It's typically constructed of stainless steel or graphite, coated with a high-temperature insulation layer (such as mineral wool, ceramic fiber blanket, or high-temperature aluminum silicate wool) to minimize heat loss. One end of the insulated main steam pipe is positioned close to the crucible outlet of the vacuum furnace, allowing tin and impurities to enter through this pipe from the top of the crucible. The other end connects directly to the inlet flange of the "primary condensing zone" (i.e., the jacketed spiral condensing coil). This insulation prevents premature condensation of tin vapor on the pipe wall due to a sudden drop in temperature before reaching the primary condensing zone.

[0072] A jacketed spiral condenser coil is a core device installed downstream of the insulated main steam pipe, used to condense tin vapor back into liquid within a temperature range of 350–400°C. It consists of an outer tube (e.g., SUS316 stainless steel) and a spirally wound inner tube. The inner tube circulates the tin vapor, while the outer tube forms a jacket space for circulating hot oil or air flow to control the temperature, maintaining a precise wall temperature of 350–400°C. The inner tube is typically helically wound, with the pitch and number of coils designed based on flow rate and heat transfer requirements. The outer jacket is maintained at a constant temperature by hot oil or electric heating tape.

[0073] In this embodiment, the coil diameter can be set to 15mm, the pitch is 20mm, the coil diameter is 60mm, and there are 5 turns in total. The inlet of the spiral condenser coil is directly connected to the outlet of the insulated main steam pipe. When the tin vapor leaves the insulated pipe, it immediately enters the jacketed spiral coil. The coil outlet extends through a short straight pipe to the cold trap branch point. The spiral structure increases the residence time of the tin vapor at 350-400°C, improving condensation efficiency and converting the majority of the tin vapor into liquid droplets. In addition, a small branch at the coil outlet guides residual gas to the cold trap, ensuring that high-vapor-pressure impurities do not mix with the liquid tin in the coil. A corresponding guide groove is installed below each spiral condenser coil. The guide groove is at an angle of approximately 30° to the coil wall, with a width of 50mm and a depth of 10mm. It is coated with an anti-stick silicon-carbon coating. A scraper with a shovel hook is installed at the guide groove inlet to automatically guide the tin droplets down the groove into the cooling tank to store the secondary tin ingots.

[0074] It should be noted that at atmospheric pressure, tin's boiling point is 2270°C. Although the vacuum within the graphite crucible is 10⁻³Pa, which lowers tin's effective boiling point, 1100°C is still relatively low compared to tin's boiling point. This means that in step 2, only a very small amount (approximately 0.01%) of tin (i.e., primary tin vapor) becomes gaseous and flows along the pipe with the high-vapor-pressure impurities.

[0075] In addition, unlike high-vapor-pressure impurities, primary tin vapor condenses into droplets before entering the cold trap, dripping back down the tube wall and gathering into secondary tin ingots in the primary condensation zone, rather than following the airflow all the way to the cold trap. High-vapor-pressure impurities, on the other hand, remain in the gas phase at 350-400°C and, unlike tin, do not condense into solids or liquids in the primary condensation zone.

[0076] Therefore, taking 5kg of pre-treated tin as an example, even though only about one ten-thousandth of the tin (about 0.5g) accumulates in the primary condensation zone to form a secondary tin ingot in a single iteration (say, 10 minutes), this 0.5g, though small, can increase its purity from 99.9% to over 99.99%. Repeating this process multiple times or accumulating multiple batches of 5kg of raw material can yield hundreds of grams of 4N-grade high-purity tin, sufficient for downstream refining or small-batch high-end applications (such as EUV lithography and semiconductor packaging).

[0077] EUV lithography requires a high-intensity light source with an extremely short wavelength (13.5 nanometers). One of the most effective methods for generating this light is to excite a high-density, high-temperature plasma, causing it to emit the required EUV photons. Tin is an irreplaceable core light source fuel in EUV lithography. By bombarding high-purity tin (in the form of droplets or solid / liquid streams) with a high-power laser to generate a high-temperature plasma, the tin ions efficiently radiate extreme ultraviolet light with a wavelength of 13.5 nm. Therefore, tin (Sn) plays a central role in extreme ultraviolet lithography (EUVL). It is currently the only material that has successfully applied high-power EUV light sources (13.5 nanometers wavelength) to mass production. Furthermore, in the semiconductor packaging process, the purity of tin directly determines the reliability, electrical performance, and long-term stability of chip interconnects.

[0078] Step S140 , placing the secondary tin ingot in a graphite crucible for vacuuming and heating, so as to iteratively distill and refine the secondary tin ingot to obtain high-purity metallic tin.

[0079] In some embodiments, the method for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention, step S140 specifically includes the following steps: Step S141 , placing the secondary silver ingot in a graphite crucible for vacuuming and heating, so as to repeatedly perform distillation and refining on the secondary tin ingot to obtain refined tin vapor.

[0080] Step S142 , condensing the refined tin vapor under argon protection to obtain a refined tin ingot, and using GDMS to detect the tin purity of the refined tin ingot, and obtaining high-purity metallic tin after the detection is qualified.

[0081] In a specific embodiment, the present invention provides a method for preparing high-purity metallic tin using vacuum distillation technology, step 4, iterative distillation and tin ingot inspection.

[0082] Specifically, after obtaining the above-mentioned secondary tin ingot, return to step 2 and iterate multiple times. Each iteration requires slowing down the heating rate so that low vapor pressure impurities are retained in the crucible. The final tin ingot is condensed into high-purity tin vapor under argon protection to form a high-purity tin ingot; GDMS is used to detect the purity of ≥99.999%. If it is qualified, it will be put into storage. If it is unqualified, the high-purity tin ingot (from multiple batches) will replace the pretreated tin material, and return to step 2 to repeat the distillation and refining to complete the closed-loop purification.

[0083] In some embodiments, the present invention provides a method for preparing high-purity metallic tin using vacuum distillation technology, wherein the jacketed spiral condenser coil has multiple condensation ports corresponding to different coils, different guide grooves, and different cooling tanks of the jacketed spiral condenser coil. The method further includes the following steps: Step S210: construct a machine learning model based on the condensation temperature, isotope ratio and tin vapor content corresponding to each of the multiple condensation ports, and determine the loss function and constraint conditions of the machine learning model according to the isotope ratio and tin vapor content.

[0084] In step S220, a machine learning model is called, and the current condensation temperature of each condensation port is used as input to output the corresponding isotope ratio of the tin element and the tin vapor content, so as to dynamically adjust the condensation temperature of each condensation port based on the isotope ratio and the tin vapor content.

[0085] The constraints are used to determine the number of iterative distillation and refining times of the tin ingot.

[0086] In some embodiments, the method for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention further includes the following steps: Step S310: When the tin purity of the refined tin ingot does not meet the preset requirements after GDMS testing, the refined tin ingot is crushed and placed in a graphite crucible for vacuuming and heating, so as to distill and refine the refined tin ingot again until the tin purity meets the preset requirements.

[0087] In a specific embodiment, the method for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention easily leads to isotope fractionation during the vacuum evaporation stage. That is, under the evaporation conditions of 10⁻³ Pa and 1100°C,¹¹ 6 Sn,¹¹ 7 The vapor pressure of lighter isotopes such as Sn is slightly higher than that of ¹²²Sn, ¹² 4For Sn, because light tin vapor enters the gas phase earlier than heavy tin vapor and is initially more easily condensed, the heavy isotope is slightly more enriched in the cold trap. However, since steps 1-4 involve numerous iterations, this slight difference accumulates and amplifies with each iteration. If the product is used for semiconductor EUV lithography or gamma-ray packaging solder balls, isotope imbalance can cause energy level shifts and thermal conductivity drift. Therefore, a machine learning model is required.

[0088] Specifically, assuming a jacketed spiral condenser coil has five turns, it typically includes at least five condensation ports: the first, second, third, fourth, and fifth condensation ports. From the above analysis, it is clear that the first condensation port has the highest concentration of lighter isotope tin vapor, exceeding that of the fifth condensation port. Meanwhile, the fifth condensation port typically contains more tin vapor enriched in heavier isotopes than the lighter isotopes. Therefore, the liquid tin collected from the five condensation ports must be mixed and adjusted based on its concentration distribution, typically measured by multi-collector thermal ionization mass spectrometry (MC-TIMS), to produce a high-purity tin ingot. However, this inevitably means that some of the collected tin vapor is wasted, its isotopic distribution precisely neutralizing the tin film at the cold trap. Therefore, machine learning is needed to minimize this waste by controlling the temperature of each condensation port.

[0089] When building a machine learning model, the input is: is the temperature of the first condensation port, the second condensation port, the third condensation port, the fourth condensation port and the fifth condensation port; the output is: The isotope ratios of the first condensation port, the second condensation port, the third condensation port, the fourth condensation port and the fifth condensation port, and the mass of the tin vapor of the first condensation port, the second condensation port, the third condensation port, the fourth condensation port and the fifth condensation port respectively.

[0090] In this embodiment, the machine learning model may be selected from XGBoost or a multi-layer perceptron (MLP), etc., which is not limited here. Since the machine learning model is common knowledge, its technical details are not repeated here.

[0091] It should be noted that based on the above machine learning model, its loss function is not difficult to infer as shown below: ; Where, is a parameter value less than 1, which is the maximum value that satisfies the following constraints. The constraints are as follows: ; Where, It is a value slightly larger than 1, usually set to 1.001, based on the actual application scenario (for example: isotope ratio, tin purity); when hour, .

[0092] It should be noted that the purity of tin determines the number of refining iterations, which in turn determines That is to say, the higher the purity, the more iterations there are. The value must be smaller: it is equivalent to spreading the effect of each iteration to The isotope ratio refers to¹¹ 6 Sn and ¹² 4 Sn content ratio. Understandable, as long as ¹¹ 6 Sn and ¹² 4 If the ratio of Sn is close to 1, then the ratio of the content of any two isotopes between the two will only be closer to 1 than the isotope ratio.

[0093] The following describes the device for preparing high-purity metallic tin using vacuum distillation technology provided by the present invention. The device for preparing high-purity metallic tin using vacuum distillation technology described below and the method for preparing high-purity metallic tin using vacuum distillation technology described above can be referenced to each other.

[0094] like Figure 2 As shown, in one embodiment, a device for preparing high-purity metallic tin using vacuum distillation technology includes a graphite crucible, a pipe, a main condensation zone and a cold trap.

[0095] The graphite crucible is located at the bottom of the vacuum furnace chamber and is used to hold pre-treated tin material.

[0096] The input end of the pipeline is connected to the output end of the graphite crucible and is divided into an insulated main steam pipe and a jacketed spiral condensing coil. The insulated main steam pipe is used to guide the tin vapor to the jacketed spiral condensing coil. The jacketed spiral condensing coil serves as the main condensing area for zoned condensation of the tin vapor.

[0097] The cold trap is connected to the output end of the main condensation zone and is used to adsorb high vapor pressure impurities remaining after flowing through the main condensation zone.

[0098] The present disclosure may be a system, method and / or computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0099] A computer-readable storage medium can be a tangible device that can hold and store instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punched card or raised structure in a groove on which instructions are stored, and any suitable combination thereof. As used herein, a computer-readable storage medium is not to be construed as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse passing through a fiber optic cable), or an electrical signal transmitted through an electrical wire.

[0100] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions to be stored in the computer-readable storage medium in each computing / processing device.

[0101] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages such as Smalltalk, C++, and conventional procedural programming languages such as "C" or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, the state information of the computer-readable program instructions is used to personalize an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), so that the electronic circuit can execute the computer-readable program instructions, thereby implementing various aspects of the present disclosure.

[0102] Various aspects of the present disclosure are described herein with reference to flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each block of the flowcharts and / or block diagrams, and combinations of blocks in the flowcharts and / or block diagrams, can be implemented by computer-readable program instructions.

[0103] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, thereby producing a machine, so that when these instructions are executed by the processor of the computer or other programmable data processing device, a device is generated that implements the functions / actions specified in one or more blocks in the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium, where these instructions cause the computer, programmable data processing device, and / or other device to operate in a specific manner. Thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing various aspects of the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0104] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operational steps are performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to implement the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0105] The flow charts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the systems, methods and computer program products according to multiple embodiments of the present disclosure. In this regard, each box in the flow chart or block diagram can represent a part of a module, program segment or instruction, and the part of the module, program segment or instruction contains one or more executable instructions for realizing the prescribed logical function. In some alternative implementations, the functions marked in the box can also occur in a sequence different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented by a dedicated hardware-based system that performs the prescribed function or action, or can be implemented by a combination of dedicated hardware and computer instructions.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-purity metallic tin using vacuum distillation technology, characterized in that: The method comprises: The tin ingot is mechanically crushed and the oxide scale is brushed off, and then vacuum dried to obtain the pretreated tin material; The pretreated tin material is placed in a graphite crucible for vacuuming and heating, so that high vapor pressure impurities are volatilized along with the tin vapor, and the high vapor pressure impurities are captured by a cold trap to obtain primary tin vapor; guiding the primary tin vapor to flow through a primary condensation zone for condensation to obtain a secondary tin ingot; The secondary tin ingot is placed in a graphite crucible for vacuuming and heating, so as to perform iterative distillation and refining on the secondary tin ingot to obtain high-purity metallic tin.

2. The method for preparing high-purity metallic tin using vacuum distillation technology according to claim 1, characterized in that: The tin ingot is mechanically crushed and the oxide scale is brushed off, and then vacuum dried to obtain the pretreated tin material, comprising: placing the tin ingot in a jaw crusher with a polyurethane liner, adjusting the gap between the movable jaws, crushing the tin ingot, and separating the iron scraps in the crushed tin ingot by magnetic separation; The crushed tin block is placed in a drum scrubber for scrubbing to remove the oxide scale on the surface of the tin block; the oxide scale includes a SnO2 / Ox layer and salt particles.

3. The method for preparing high-purity metallic tin using vacuum distillation technology according to claim 2, characterized in that: The tin ingot is mechanically crushed and the oxide scale is brushed off, and the pretreated tin material is obtained after vacuum drying, and the method further comprises: Placing the tin block after the oxide scale is removed in a double-chamber vacuum oven, adjusting the temperature of the double-chamber vacuum oven, and performing a vacuum drying process on the tin block to remove bound water and air in the air gap of the tin block; The vacuum-dried tin blocks are screened through a stainless steel vibrating screen to retain the tin blocks that meet the particle size requirements and put them into an argon-filled temporary storage hopper to obtain the pretreated tin material, and the tin blocks that do not meet the particle size requirements are subjected to secondary crushing treatment.

4. The method for preparing high-purity metallic tin using vacuum distillation technology according to claim 1, characterized in that: The pretreated tin material is placed in a graphite crucible for vacuuming and heating to volatilize high vapor pressure impurities along with the tin vapor, and the high vapor pressure impurities are captured by a cold trap to obtain primary tin vapor, comprising: The pretreated tin material is placed in a graphite crucible, and a graphite cover is covered on the top of the graphite crucible containing the pretreated tin material to seal it, and a vacuum treatment is performed; Inserting a platinum-rhodium thermocouple into a temperature control hole on the side wall of the graphite crucible to provide real-time feedback of temperature data, and uniformly heating the temperature to a preset temperature according to a heating program curve to perform constant temperature heating, thereby heating the pretreated tin material from a solid phase to a liquid phase and a gas phase; driving the tin molecules in the liquid phase and the gas phase and the high vapor pressure impurities to synchronously separate from the liquid phase by vapor pressure to separate the primary tin vapor; The graphite cover on the top of the graphite crucible is connected to the vacuum furnace chamber flange through a graphite ring sealing ring, and the high vapor pressure impurities and tin molecules enter the pipeline after leaving the liquid phase. A graphite sealing ring is provided at the joint between the pipeline and the vacuum furnace chamber to isolate air intrusion.

5. The method for preparing high-purity metallic tin using vacuum distillation technology according to claim 4, characterized in that: The pipeline is composed of an insulated main steam pipe and a jacketed spiral condensing coil. The insulated main steam pipe is made of stainless steel or graphite and is coated with a high-temperature resistant insulation layer. One end of the insulated main steam pipe is connected to the output port of the graphite crucible, and the other end is connected to the input port of the jacketed spiral condensing coil. The jacketed spiral condensing coil is the main condensing area, which is divided into an inner tube and an outer tube. The inner tube is used to circulate the primary tin vapor, and the outer tube is used to circulate hot oil or blow air to control the temperature, so as to control the temperature of the inner tube wall within a preset condensing temperature range.

6. The method for preparing high-purity metallic tin using vacuum distillation technology according to claim 5, characterized in that: The step of guiding the primary tin vapor to flow through the primary condensation zone for condensation to obtain a secondary tin ingot comprises: guiding the primary tin vapor to flow through the insulated main steam pipe and then into the jacketed spiral condensing coil, controlling the inner tube wall temperature of the jacketed spiral condensing coil to be within a preset condensing temperature range, and condensing the primary tin vapor to obtain liquid tin and residual gas; directing the residual gas through the branch of the jacketed spiral condensing coil into a cold trap to separate high vapor pressure impurities; A guide groove is provided at the bottom end of each spiral condensing coil of the jacketed spiral condensing coil, and a shovel hook type scraper is provided at the input end of the guide groove for guiding the liquid tin to flow into the cooling tank, and the secondary tin ingot is obtained after cooling and storage.

7. The method for preparing high-purity metallic tin using vacuum distillation technology according to claim 5, characterized in that: The jacketed spiral condensing coil has a plurality of condensing ports, which respectively correspond to different coils, different guide grooves, and different cooling tanks of the jacketed spiral condensing coil; the method further comprises: Constructing a machine learning model based on the condensation temperatures, isotope ratios, and tin vapor contents corresponding to each of the plurality of condensation ports, and determining a loss function and constraints of the machine learning model based on the isotope ratios and the tin vapor contents; calling the machine learning model, taking the current condensation temperature of each condensation port as input, and outputting the corresponding isotope ratio of the tin element and the tin vapor content, so as to dynamically adjust the condensation temperature of each condensation port based on the isotope ratio and the tin vapor content; The constraint condition is used to determine the number of iterative distillation and refining times of the tin ingot.

8. The method for preparing high-purity metallic tin using vacuum distillation technology according to claim 1, characterized in that: The secondary tin ingot is placed in a graphite crucible for vacuuming and heating to perform iterative distillation and refining on the secondary tin ingot to obtain high-purity metallic tin, comprising: placing the secondary silver ingot in a graphite crucible for vacuuming and heating, so as to repeatedly distill and refine the secondary tin ingot to obtain refined tin vapor; The refined tin vapor is condensed under argon protection to obtain a refined tin ingot, and the tin purity of the refined tin ingot is tested by GDMS. After passing the test, the high-purity metallic tin is obtained.

9. The method for preparing high-purity metallic tin using vacuum distillation technology according to claim 8, characterized in that: The method further comprises: When the tin purity of the refined tin ingot does not meet the preset requirements after GDMS testing, the refined tin ingot is crushed and placed in a graphite crucible for vacuuming and heating, so as to distill and refine the refined tin ingot again until the tin purity meets the preset requirements.

10. A device for preparing high-purity metallic tin using vacuum distillation technology, characterized in that: For implementing the method for preparing high-purity metallic tin using vacuum distillation technology according to any one of claims 1 to 9, the device comprises a graphite crucible, a pipe, a main condensation zone and a cold trap; The graphite crucible is located at the bottom of the vacuum furnace chamber and is used to hold the pre-treated tin material; The input end of the pipeline is connected to the output end of the graphite crucible, and is divided into an insulated main steam pipe and a jacketed spiral condensing coil. The insulated main steam pipe is used to guide the tin vapor to the jacketed spiral condensing coil. The jacketed spiral condensing coil serves as the main condensing zone and is used to condense the tin vapor in different zones. The cold trap is connected to the output end of the main condensation zone and is used to adsorb high vapor pressure impurities remaining after the impurities flow through the main condensation zone.

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